Synthesis, Characterization, and Reactivity of Sulfido- and Selenidomolybdenum(IV) Porphyrin Complexes. X-ray Structure of Sulfido(5,10,15,20-tetratolylporphyrinato)molybdenum(IV)
Reprinted (adapted) with permission from Inorganic Chemistry 34 (1995): 3485, doi:10.1021/ic00117a017. Copyright 1995 American Chemical Society.
Treatment of (TTP)Mo(PhC=CPh) (TIP= meso-tetra-p-tolylporphyrinato) with Ss or CpzTiSs in toluene results in the formation of (TTP)Mo=S. The sulfide complex may also be prepared from the treatment of (TTP)MoCb with LizS in THF. Similarly, a terminal selenide complex may be prepared from treatment of (TTP)MoCb with Na2Se. The structure of (TTP)Mo=S has been determined by single-crystal X-ray diffraction analysis (triclinic, PI. a = 12.735(2) A, b = 13.521(2) A, c = 13.920(2) A, a = 74.76(1)0 , f3 = 78.95(1)0 , y = 80.85(1)0 , v = 2254.7(5) A3, Z = 2, R = 3.1 %, Rw = 4.2% ). Complete sulfur atom transfer occurs between (TTP)Mo(PhC=CPh) and (TTP)Sn=S to give (TTP)Mo=S, (TTP)Sn", and PhC=CPh. The net result is a formal two-electron redox process that occurs irreversibly between Sn(IV) and Mo(II). Correspondingly, no reaction is observed between (TTP)Mo=S and (TTP)Sn" in the presence of excess PhC=CPh. The analogous treatment of (TTP)Mo(PhC=CPh) with (TTP)Sn=Se results in the reversible exchange of a selenium ligand to form (TTP)Mo=Se, (TTP)Sn", and PhC=CPh. When treated with excess PPh3, the sulfido or selenido complex is reduced to (TTP)Mo(PPh3h with formation of either Ph3P=S or Ph3P=Se. However, when (TTP)Mo=S or (TTP)Mo=Se is reduced with PPh3 in the presence of PhC=CPh, (TTP)Mo(PhC=CPh) is formed. The alkyne ligand of (TTP)Mo(PhC=CPh) may be displaced by 4-picoline to give trans-(TTP)Mo(4-picoline)2. Ligand preference for the porphyrin Mo(II) center is thus PPh3 < PhC=CPh < 4-picoline.